Problem with stopping LS server in Linux

I managed to set up a LS server in Linux and it run well, but when I execute the shells to restart or stop it emits an error as follows :

Stopping Lightstreamer Server...
Communication error
java.io.EOFException
at java.io.ObjectInputStream$PeekInputStream.readFull y(ObjectInputStream.java:2228)
at java.io.ObjectInputStream$BlockDataInputStream.rea dShort(ObjectInputStream.java:2694)
at java.io.ObjectInputStream.readStreamHeader(ObjectI nputStream.java:761)
at java.io.ObjectInputStream.<init>(ObjectInputStream .java:277)
at com.sun.jmx.remote.socket.SocketConnection$ObjectI nputStreamWithLoader.<init>(SocketConnection.java: 354)
at com.sun.jmx.remote.socket.SocketConnection.readMes sage(SocketConnection.java:204)
at com.sun.jmx.remote.opt.security.AdminClient.connec tionOpen(AdminClient.java:57)
at com.sun.jmx.remote.generic.ClientSynchroMessageCon nectionImpl.connect(ClientSynchroMessageConnection Impl.java:73)
at javax.management.remote.generic.GenericConnector.c onnect(GenericConnector.java:169)
at javax.management.remote.jmxmp.JMXMPConnector.conne ct(JMXMPConnector.java:117)
at javax.management.remote.JMXConnectorFactory.connec t(JMXConnectorFactory.java:248)
at com.lightstreamer.f.q.<init>(q.java)
at com.lightstreamer.LS_Stop.a(LS_Stop.java)
at com.lightstreamer.LS_Stop.main(LS_Stop.java)
Shutdown request could not be sent to remote Server
Do I miss something while installing LS server ?

The restart and stop scripts try to connect to Lightstreamer Server on port 9999 (or the port specified in the jmxmp_connector_port element within lightstreamer_conf.xml). Perhaps you have some personal firewall blocking this connection?